It is already well known to provide quick coupling devices on pipes and ducts through which a fluid flows for the purpose of providing a sealed connection either between two pipes or ducts connected end-to-end, or else between a pipe and a fluid inlet or outlet end-fitting or tube. These devices have the advantage of providing a sealed connection by means of a movement which is very simple, e.g. translation or rotation through one fourth of a turn.
However, it may happen that this motion is not carried right through so that the quick coupling device is not locked in its correct coupling position. In such cases, vibration, any kind of movement in the pipe, or a change in pressure of the fluid can cause the quick coupling device to come apart immediately, thereby separating the interconnected pipes and giving rise to large quantities of fluid leakage.
Such accidents are particularly likely to occur on manufacturing lines which are automated to a greater or lesser extent, e.g. in the car industry.
The object of the invention is to provide a quick coupling device suitable for providing immediate visual verification that the device has been correctly coupled.